function add(){
    var num1 = parseInt(document.getElementById("num1").value);
    var num2 = parseInt(document.getElementById("num2").value);
    var result = num1+num2;
    document.getElementById("result").value = result;
}
function jian(){
    var num1 = parseInt(document.getElementById("num1").value);
    var num2 = parseInt(document.getElementById("num2").value);
    var result = num1-num2;
    document.getElementById("result").value = result;
}
function cheng(){
    var num1 = parseInt(document.getElementById("num1").value);
    var num2 = parseInt(document.getElementById("num2").value);
    var result = num1*+num2;
    document.getElementById("result").value = result;
}
function chu(){
    var num1 = parseInt(document.getElementById("num1").value);
    var num2 = parseInt(document.getElementById("num2").value);
    var result = num1/+num2;
    document.getElementById("result").value = result;
}